This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Much of this work targets on AFB1 risk reduction. We have used the trout model to identify chlorophyllin (CHL), a food-grade derivative of chlorophyll (Chl), as a potent blocking agent against AFB1. To pursue the promise of chlorophylls and derivatives as blocking agents, we will compare the efficacy of chlorophyllin (CHL) and natural chlorophylls (Chl) in cancer chemoprevention and humans. Both agents exert antimutagenesis behavior in vitro against a wide range of carcinogens. Our guiding hypothesis is that chlorins protect in vivo primarily via reduction of carcinogen uptake and bioavailability. We propose to test our central hypothesis in humans using 14C-AFB1. Accelerated Mass Spectrometry (AMS) of body fluids following ingestion of 14C-AFB1 in the nCi/ng dose range should allow us to examine CHL and Chl effects on aflatoxin bioavailability with adequate sensitivity and negligible risk.